In mid-February, Kenai Peninsula residents began developing symptoms similar to a campylobacter infection — diarrhea, vomiting, stomach pains and fever, according the health department. The illness can lead to death in young children or those with compromised immune systems.

As of March 22, there have been 34 cases of illnesses, and in all the cases, the individuals have had associations with Peninsula Dairy, said Brian Yablon, an epidemiologist for the Alaska Section of Epidemiology. Seven of the 34 cases have been confirmed in a lab as campylobacter infection, he said. No one has died from the infection, he said.

The Campylobacter infection is a common problem on farms, said Bob Gerlach, state veterinarian.

More than 90 percent of dairy farms in the Lower 48 owned cows that tested positive for the campylobacter bacteria, according to a National Animal Health Monitoring System study from the United States Department of Agriculture.

Gerlach said farm vegetables contaminated with feces of an infected animal can also carry the bacteria.

“It’s in most of your farms,” Byers said. “Dogs. Cats. Birds. It can come on your vegetables outside by the birds crapping on them.”

Raw milk dairy farms are, however, at a greater risk for spreading the campylobacter as their milk is not heated to kill the bacteria, according to the health department.

After the state health department linked the outbreak to Byers’ farm, it collected fecal and milk samples from his cows. Lab results found three strains of campylobacter from samples collected at his farm, but none matched the confirmed strains that made people sick, Gerlach said.

“It’s not unusual that you may find one strain of campylobacter there and it may get replaced by another strain that (the cows) pick up in the environment,” he said.

In cold climates different strains of the bacteria can cycle through a farm quickly as they die out, he said. That could have been what happened on Byers’ farm, Gerlach said.

While it is illegal to sell raw milk, selling shares of a cow that produces the milk — Byers’ method — is legal, and the health department cannot shut him down.

Following the initial signs of the outbreak, the health department contacted Byers’ shareholders to warm them of the risk associated with consuming raw milk, Yablon said.

“We tried to call everybody that we could find a number for,” he said.

About a fourth of the shareholders called said they stopped drinking the milk because of the infection. Others said they still buy the milk but pasteurize it at home, “and other people have decided to keep doing exactly what they’ve been doing,” Yablon said.

Byers said he was initially worried for his business. He said the health department was using “scare tactics” to erode his customer base.

“But their scare isn’t going too far,” he said.

His customers started calling to tell him “We’re hanging in with you,” he said.

“It’s just a little bump in the trail and we’re going to keep on going,” he said.